PURPOSE: To suppress thickness variation in the transverse direction to an extremely small quantity by arranging work rolls so that the barrel end side of the increasing side of the roll diameter of backup rolls and the barrel end side having tapered parts of the work rolls are made to the same side.

CONSTITUTION: The backup rolls 11a and 11b are given profiles of a specified bolt shape cross section on the roll radius deviation and have mechanisms shiftable in the axial direction. The work rolls 12a and 12b are provided with the tapered parts 15a and 15b on the barrel sides of the recessed part profile sides of the backup rolls and have mechanisms shiftable in the axial direction in a specified stroke. Consequently, a sheet profile can be controlled freely and rolling of sheet material with little thickness variation in the transverse direction is made possible.